The point can perhaps be made in an even simpler way in response to Johnson's
claim about the creatow who supposedly "left his fingerprints all over the
evidence."
A fingerprint left at the scene of a crime of course identifies the criminal
only if you have an independent sample of someone's fingerprint with which it
can be matched. The ID argument assumes that we have some a priori knowledge
of the "fingerprint" of the Designer.

Many believing scientists (e.g. Owen Gingerich in God's Universe) start with
the a priori conviction that God is the Creator/Designer, and do science to
discover what His "fingerprints" look like. They don't claim to know what they
look like a priori; they go where the data leads.

Much of ID switches the order, starting with a priori assumptions of a
designer's "fingerprints", and using this to try to explicitly show that there was a
designer. But how do we know a priori what his "fingerprints" look like? We
get some hints from Scripture and from previous scientific discovery, but we
really don't know for sure until after the science is done, so the approach
becomes somewhat circular.